The one problem going for Rollins right now is that he's being booked as a heel who constantly needs help winning. When it comes to top level heels, for some strange reason, Vince LOVES for them to look vulnerable and unable to get the job done on their own. I have no problem with Rollins cheating, heels are supposed to cheat, but all the various interference is too much sometimes. If Rollins is to cheat, let him pull some tights, let him hit a guy with a foreign object, give him a low blow when the ref isn't looking, but stop with the incompetent stooges, Big Show, Luke Harper or whoever keep interfering in the matches.
I see a couple of possible scenarios:
1. Reigns defeats Brock Lesnar to win the title at WrestleMania XXXI, Rollins cashes in and steals the title. The next night on Raw, both Reigns & Lesnar want their title matches and a triple threat bout is made featuring Lesnar's first match on television. Reigns & Lesnar ultimately keep getting in each other's way, Rollins retains, Lesnar leaves WWE and a feud between Reigns & Rollins extends into the summer, possibly culminating at SummerSlam.
2. Reigns wins at WrestleMania XXXI, Lesnar gets his rematch on Raw the next night, Reigns retains and then Rollins successfully cashes in. This way, Reigns gets his big WrestleMania moment, Raw gets a very special main event the next night and ultimately a new champion with Rollins & Reigns feuding throughout the summer for the strap.